ktm240z

iTrader: (1)

I have a 1972 240z with a 1998 LS1. The car's been running great for 2 years until recently. About 3 months ago I noticed that the car would fall on its face when moderately accelerating from a stop light. All voltage would be cut for a split second and then the car would recover. I was also having issues with my alternator gradually losing voltage over time and decided to replace it and hoped that it might solve the other issue as well.

No dice. When I took the car to CMS to get tuned Rayn noticed that the MAF signal would drop to zero and then immediately recover when moderately accelerating but it would only do it in first gear (4L60E). All of the other gears were fine.

I checked for loose connections (but those should affect all gears) and verified voltage at the MAF (12v and 5v).

I cannot figure this one out for the life of me. Today when I was out for a cruise it fell on its face again in 1st gear, but when it recovered the engine was reving at 2000 rpm but there was no forward progress. I backed off the throttle and when I gave the car gas again, it had that "rich" exhaust note and then backfired. After that it was fine and took off normally.

This only occurs when accelerating moderately from a stop in 1st gear.

I am baffled.

joecar

Is your battery loose, or does your battery have a loose plates internally...?

ktm240z

iTrader: (1)

Joe, thanks for the response. The battery is quite secure and its an AGM that I relocated to the rear of the car. I've been traveling quite a bit recently and have not had a good chance to spend a lot of time trouble-shooting the issue.

I hope to get some time this weekend but we'll see.

ktm240z

iTrader: (1)

Update: I had time today to go out for a quick trouble-shooting drive. I turned the radio on to act as an audible signal to determine if I lost all power when the car acted up. As I punched it from a light the radio turned completely off and then immediate back on as the car fell on its face.

Sounds like a short somewhere with the main power supply. I could have sworn before that the radio stayed on when I described the problem above but I guess I was mistaken.

Quick question, does the PCM only receive its operating power from the orange constant hot wire or does one of the pink wires also provide power? If the orange wire loses power, does that basically turn the PCM off?

Thanks.

2002FirehawkNBM

iTrader: (2)

im having a similar issue with mine. i changed mine over to the 4 inch ls3 style maf that slides in. it worked fine for about three months, changed intakes and on the way home it did exactly as your car is doing. But was in all gears.

Being told it is a broken wire from the maf connector back to the pcm. Which I suppose it could be but as you did with checking the 12v and the 5v at the wires and connectors we got the same results.

For the time being its in sd to drive it. I know so many of the old fbodys were know to have bad wiring it was a complaint, but might be a place to start. That is if you reused the factory harness and such.

Good luck to ya..

ktm240z

iTrader: (1)

Closing this issue out.

The issue turned out to be a short. On the 240z swap, the Camaro alternator mount does not provide a lot of clearance between the battery lug and the stock 240z cradle. When I reattached my battery cable a few months ago, the rubber boot that covers terminal on the battery cable was resting against the cradle. Over time the boot was punctured and the lug would contact the cradle under hard acceleration.